Nokia Siemens is expected to delay its purchase of Motorola's wireless network infrastructure assets after the company disclosed it has not obtained the necessary regulatory clearance for the deal.

In a statement on Tuesday, the Finnish-German company said the Anti-Monopoly Bureau of China's Ministry of Commerce is still reviewing the proposed transaction. The $1.2bn (£775m) deal was announced in July, and had been originally targeted to close by year-end.

Rajeev Suri, Nokia Siemens' chief executive, said in the statement the delay was "disappointing", but added that the company expects to finalise the acquisition in early 2011.

"We are continuing to work closely with the authority in China to finalise the clearance process in that country," he said. "We recognise its efforts in addressing this case as a matter of importance."